General Keys to Families and Special Groups

SEED PLANT FAMILY KEY - Seed plants (conifers and flowering plants); plants with seeds, born either in cones or in ovaries formed in flowers.

This series of keys is intended to lead one to the family, or sometimes directly to the genus or species, of an unknown plant. Therefore, the keys are based on the most reliable and easily observed characters for that purpose; only rarely (and incidentally) do they reflect the natural relationships and classification of the families. Diverse families (or their component genera and species) will usually key down at more than one place, so the keys often cannot be “worked backwards” to gain a concise description of the diagnostic features of a family.

Furthermore, the keys accommodate a number of easy misinterpretations that a beginner might make (e.g., considering the 3 bracts of Hepatica to be sepals; or believing a series of perianth parts to be absent when in fact the calyx or corolla is present but either very tiny or very early deciduous; or interpreting a very deeply lobed corolla as composed of separate petals). And they accommodate some ambiguities on the part of the plants themselves (e.g., if the ovary is only partly inferior, it should key under both “superior” and “inferior”; or if the perianth is only slightly bilaterally symmetrical it should key also under “regular”). However, plant taxa are composed of living organisms, and hence are variable; there will always be some individuals so “far out” as to defy identification by any key. Keys are a tool to help you learn the plants, not a subsitute for knowing them.

The keys are designed to cover only seed-plants known from Michigan and may not work for other species in the same families or genera. Except for a few true aquatic species in key A, ferns and their “allies” (horsetails, clubmosses, etc.) are in a separate key. Ordinarily, flowers are required for use of the seed-plant keys; the diversity of plants covered simply does not allow a key based on vegetative characters alone. Many aquatic plants are, however, seen but rarely in flower and even then the flowers are often much reduced and obscure; but they can be identified vegetatively. Therefore, many of these plants are disposed of in Key A, the first of the individual keys.

The summary of characters at the beginning of each individual key is not always exhaustive; e.g., plants which will key as aquatics (Key A) or with neither green color nor developed leaves (Key C) may not run under later keys even though the later summary headings do not explicitly exclude such plants. Nevertheless, before forging ahead in any of the individual keys, the user should find it helpful to read the summary, as a reminder of how one arrived there and as an opportunity to confirm accurate reading thus far.

Unless explicitly stated to the contrary, references to “flowers” are to normal open flowers (showy or obscure) and not to cleistogamous flowers (fertilized and setting seed while remaining in “bud”). As always, keys should be read carefully. For instance, if the perianth (sepals and/or petals) is said to be regular (radially symmetrical), that does not necessarily mean that the reproductive parts (stamens and/or pistils) are also regular.

4. Plants resembling a moss (almost 2-dimensional) or new growth of a Juniper or a miniature clubmoss. Spores (of two sizes) hidden beneath the expanded parts of green leaves (sporophylls) in fertile stems that are often the only erect part of the plant

1. Leaves more than 1 cm long (often much longer), solitary or relatively few in number (except in the aquatic Isoetes); if more numerous, then borne singly and more or less spaced out along a rhizome, or forming a crown or tuft

6. Photosynthetic blades not divided or clover-like, not floating on water

7. Sporangia fused laterally into 2-rowed, long-stalked spike-like structure (synangium) and opening by double rows of pores or slits, this borne on a stalk separate from the sterile blade; vegetative part of leaf entire

9. Spores in globose sporangia 0.5–1 mm in diameter, opening without an annulus (band of specialized cells) and containing hundreds to thousands of spores; indusia absent; borne singly on special fertile branches that turn yellow and eventually shrivel at or before spore release [do not mistake the fertile fronds of the Onocleaceae, with hard, rolled up pinnae containing many tiny sporangia for these larger globose sporangial structures]

10. Leaves usually single per plant, often less than 30 cm tall; fertile portions of leaves (normally long-stalked) inserted near base of sterile portion; spores whitish or yellow, thousands per sporangium

10. Leaves several to many per plant, borne in a cluster, normally more than 30 cm long; fertile portion of leaves apical, in center of a leaf, or leaves dimorphic with sporangia on separate fertile leaves; spores green, hundreds per sporangium

9. Spores in sporangia (excluding stalks) less than 0.4 mm, usually containing 16–64 spores, opening with an annulus; indusia present or absent; sporangia borne in round or elongated clusters (sori) borne on the undersides or along the margins of regular, green blades or sometimes inside hard, inrolled leaf tissue on separate non-green but hard and persistent fertile fronds

11. Sori borne on regular green leaves, these sometimes somewhat different in form from the vegetative leaves, but not becoming hard, brown, and persistent

12. Sori elongate, arranged end to end in one row on each side of the midrib of pinnatifid or pinnate blades to form a chain; species of acid bogs and adjacent open swamps with long creeping rhizomes bearing well separated leaves

22. Blade margins (especially at the apex of the pinnules) with teeth sharply acute, acuminate, or contracted to a bristle-like tip (except in D. fragrans and D. marginalis); fronds firm, long persistent into the fall or even evergreen; indusia peltate or attached laterally at one point, ± persistent

22. Blade margins with blunt teeth; fronds delicate, arising early in the season and often deciduous by late summer; indusia hood-like, attached on one side and arching over the sorus, fragile and quickly disintegrating

The introductory key below leads sometimes to a family but mostly to the 15 individual keys (A through O) which follow. When there are several genera in a family and only one of them will run at a given lead in a key, the name of the genus (or even of a species) is usually stated.

1. Plants strictly aquatic, the leaves or plant body entirely submersed or floating on the surface of the water (at most, the inflorescence and bracts, not leaves, held above the surface except in a few free floating species)[1]

1. Plants with at least some leaves (or stem if plant apparently leafless) above the water (but not free floating) or plants strictly terrestrial

2. Plants woody (trees, shrubs, and woody vines), with erect, trailing, or viny above-ground stems living through the winter and continuing to grow the next season [hence, leaves may be evergreen or deciduous]

2. Plants herbaceous, the perennial parts, if any, below or on the surface of the ground (to which the stems die back each year), not producing woody stems which survive the winter well above ground [hence, without aerial evergreen leaves (although there may be basal winter-green leaves)]

3. Plant lacking green color (often wholly parasitic or saprophytic) and the leaves none at flowering time or reduced to tiny scales)[2]

5. Perianth parts (2), 3, (4), or 6 (never 5) and leaves (or other green photosynthetic parts when leaves are absent or reduced) parallel-veined (the 3 or more main veins running from base of blade to apex and ± parallel, with or without minute cross-veins), entire, simple[4]

5. Perianth parts various (often 5) but leaves netted-veined (or with only the midvein conspicuous), entire or toothed, simple or compound (the main veins, if more than 1, branching and ± reticulate)[5]

6. Inflorescence a dense “head” (either a true head or a spadix), consisting of few to many small sessile flowers on a common receptacle (not merely an elongate spike), subtended by 1 or more small or large bracts

8. Inflorescence of “false flowers” consisting of small cup-like structures (uniform in texture and not composed of separate parts like bracts or scales) each bearing 1–5 glands on its rim (sometimes with additional petaloid appendages) and including 2 or more stamens and 1 central stalked 3-lobed pistil (which ripens into an exserted, 3-lobed capsule); sap milky[6]

(Aquatic Plants with All Leaves Floating or Submersed, or Plants Free Floating)

1. Plants without distinct stem and leaves, free-floating at or below surface of water (except where stranded by drop in water level), the segments (internodes) small (up to 15 mm, but in most species much smaller), often remaining attached where budded from parent plant

5. Plants with floating leaves present (blades, or at least their terminal portions, floating on the surface of the water, usually ± smooth and firm in texture, especially compared with submersed leaves, or submersed leaves none)

6. Blades of some or all floating leaves on a plant sagittate or deeply lobed at base, or compound, or peltate

14. Floating leaves larger, not in a rosette; submersed leaves alternate, basal, or absent; flowers mostly in a terminal inflorescence

15. Leaves narrow and ribbon-like, the blades many times as long as broad, without distinct petiole (though in some species a sheath surrounds the stem)

16. Leaves ± rounded at tip (even if tapered), the floating portion smooth and shiny, somewhat yellow-green to bright green when fresh, occasionally keeled but midvein scarcely if at all more prominent than others; leaf not differentiated into blade and sheath, the submersed portion similar to the floating but more evidently with a fine closely checkered pattern; flowers and fruit in spherical heads

16. Leaves sharply acute at tip, the floating portion rather dull, ± blue-green when fresh, with midrib; leaf including a sheath around stem and a membranous ligule at junction of sheath and blade; flowers and fruit in paniculate spikelets

25. Midvein not evident, all veins of essentially equal prominence, with the tiny cross-veins giving a checkered appearance to the leaf, which is thus uniformly marked with minute rectangular cells ca. 1–2 mm long or smaller

25. Midvein (and usually some additional longitudinal veins) evident, the veins not all of equal prominence, not dividing the leaf into minute rectangular cells

26. Leaves with the central third (or more) of distinctly different pattern (more densely reticulate) than the two marginal zones; plants dioecious, the staminate flowers eventually liberated from a dense inflorescence submersed at base of plant, the pistillate solitary on a long ± spiraled stalk which reaches the surface of the water; plants without milky juice

21. Leaves (or similar vegetative stems) filiform or terete or only slightly flattened (especially basally), elongate and limp to short and quill-like, less than twice as broad as thick

27. Major erect structures solitary, spaced along a simple or branched delicate rhizome, consisting either of rather yellowish stems bearing minute alternate bumps as leaves or of filiform leaves mostly buried in the substrate and with a few minute bladder-like organs

27. Major erect structures solitary to densely tufted, consisting of filiform or quill-like leaves or stems, with neither alternate bumps or bladders

29. Leaves very limp (retaining no stiffness when removed from water and hence irregularly sinuate, bent, or matted on herbarium specimens) though a stiffer straight stem may also be present, mostly more than 20 cm long, ca. 0.2–1 mm in diameter

30. Leaves (actually vegetative stems) terete their entire length, not expanded basally nor sheathing each other, but each separate and closely surrounded at base for ca. (0.6–) 1 cm or more by a very delicate membranous tubular sheath (this sometimes requiring careful dissection to distinguish); rhizome less than 2 mm in diameter; inflorescence (rare on plants otherwise entirely submersed) a single strictly terminal spikelet

31. Rhizome reddish, at least on older portions; leaves (vegetative culms) mostly over 20 cm long, very limp; fertile culm triangular in cross-section on emersed portion, much larger in diameter than the hair-like vegetative culms, but spikelet no thicker than culm

30. Leaves slightly expanded basally for ca. (0.7–) 2–10 cm, sheathing the next inner leaf at least dorsally (usually the sheath continued ventrally as an almost invisible membrane), with tiny ligule or pair of auricles at the summit; rhizome various; inflorescence a lateral spikelet or terminal cyme

32. Leaf somewhat flattened or grooved ventrally for at least a few cm above the sheath (± crescent-shaped in cross-section), with 1–5 longitudinal nerves evident, the tiny cross-veins connecting between nerves but not extending entirely across the leaf; sheath with a tiny ligule at summit; rhizome less than 2 mm in diameter; inflorescence a solitary lateral spikelet on a stiff wiry stem just above or near the surface of the water; flowers without petals and sepals; fruit an achene

32. Leaf terete above sheath, with no evident longitudinal veins, but numerous definite septa extending entirely across the blade (which shrinks between septa on drying); sheath with a minute pair of auricles at summit; rhizome ca. 2–5 mm thick; inflorescence an open cyme of many several-flowered heads on a very stout stem (several mm in diameter, over 50 cm tall); flowers with 6 tepals; fruit a capsule

29. Leaves usually firm (retaining stiffness when removed from water and hence straight or with an even curve in herbarium specimens), less (in most species much less) than 20 cm long, of various diameter

33. Leaves filiform throughout, not broader basally nor sheathing each other, solitary (rarely) or in small tufts along a filiform whitish rhizome, each leaf (actually a vegetative stem) closely surrounded at its base for ca. 6 mm or more by a very delicate membranous tubular sheath (this sometimes requiring careful dissection to distinguish); inflorescence (rare on completely submersed plants) a single terminal spikelet

33. Leaves linear or tapered from base to apex, or if otherwise uniformly filiform then expanded at base or sheathing each other, without individual tubular sheaths as described above; inflorescence various

36. Leaves gradually and slightly expanded or grooved on one side at a somewhat sheathing base but not composed of 4 tubes nor enclosing sporangia and no corm-like stem present; plants (except Subularia) not flowering when submersed but only on wet shores

37. Leaves ± terete, scarcely or no wider at base than at middle, of ± uniform width at least to the middle (or even slightly thicker there before tapering to apex); plants with rhizomes or stolons at, near, or above surface of substrate

44. Petiole absent or nearly so, the blade pectinate (with straight central axis following midrib, once-pinnatifid or comb-like on both sides) or much dissected or soon forking once or twice; flowers inconspicuous or yellow

45. Leaves once or twice dichotomously forked, the segments usually sparsely toothed along one edge; flowers inconspicuous, axillary, submersed

49. Petioles and stipular sheaths absent; plants with small stalked bladders on leaves or on separate branches; flowers bilaterally symmetrical, yellow or purplish, with a single pistil producing a capsule

66. Leaves filiform to linear-lanceolate, ± expanded at very base, acute or apiculate at apex, at least 6 times as long as wide, minutely apiculate to conspicuously toothed on margins, usually subtending axillary tufts of leaves and/or flowers or ellipsoid fruit; plant without glands on surface

67. Stems forming moss-like mats but the erect or ascending tips (above rooted nodes) less than 3 cm long; leaves with at most 1 weak nerve; stipules minute but usually evident with some leaves; flowers axillary, inconspicuous

Included here are all plants that are woody in the traditional sense; forming above ground twigs with secondary growth and winter buds. A few soft-wooded species with greenish stems such as Pachysandra and Ruta are also included. These will be keyed as herbaceous plants as well. This key also includes small evergreen trailers such Vinca, Linnaea, and Mitchella.

1. Leaves scale-like (ca. 4 mm or less long and often appressed/imbricate) or needle-like (stiff and filiform to narrowly linear, less than 2.7 mm broad), evergreen (except in Tamaricaceae and Larix in Pinaceae)

9. Seeds borne on scales of a dry woody cone; leaves flattened or not (but if so, not strongly decurrent, readily falling when dry, not 2-ranked, except the deciduous Taxodium, and/or with white lines beneath)

10. Leaves evergreen (except Larix with leaves spirally arranged), arranged in clusters, spiraled around the stem, or in flattened 2-ranked sprays; cones slightly to very much longer than wide, the cone scales flattened

47. Calyx lobes up to 1.5 mm long and broadly triangular to broadly rounded or virtually absent; corolla rotate (flat with very short tube); style very short or essentially absent; fruit fleshy with one pit

104. Leaves with lateral veins curved and ascending, weaker and the branches anastomosing near the margins; flowers usually unisexual, the perianth lobed nearly or quite to the base; ovary not flattened, fruit a drupe

3. Inflorescence not a spadix (if flowers in a head, this with neither an elongate fleshy axis nor a conspicuous subtending spathe); leaves simple, rarely net-veined (in Smilax ecirrata, Trillium, and some Alismataceae)

5. Perianth much reduced: absent, or composed solely of bristles (these small and stiff or elongate and cottony), or of chaffy or scale-like parts, never conspicuously petaloid

6. Individual flowers subtended by 1 or 2 scales; leaves ± elongate, grass-like, usually with a sheath at the base surrounding the stem; fruit a 1-seeded grain or nutlet (achene)

7. Each fertile flower subtended by a single scale (others may be at base of spikelet); sheaths of leaves closed (margins connate); stems frequently triangular (but 4–several-angled or terete in many species), usually solid; leaves usually 3-ranked (especially in a species with terete hollow stem); stamens with filament attached to end of anther; fruit a definitely 2- or 3-sided (rarely nearly terete) nutlet

19. Petals blue, purple, white, or pink; flowers in a more open or larger inflorescence

20. Pistils several in each flower, each developing into an achene; stamens 6–many; flowers unisexual or bisexual; petals white or pinkish; leaves often broadly elliptic or sagittate, usually ± net-veined, all basal

44. Perianth white, 5–10 mm long when mature; leaves lanceolate to elliptic (longest leaves less than 20 times as long as wide or over 1 cm wide, or both); plants not bulbous

45. Leaves elliptic, the widest 2–6 cm broad; stems up to 35 cm tall, about equaling or shorter than the leaves; flowers nodding, on pedicels longer than the subtending bracts; perianth smooth on outside; fruit a berry

45. Leaves narrowly lanceolate or oblanceolate, the widest less than 2 cm broad; stems over 40 cm tall, much surpassing the leaves; flowers ascending on pedicels shorter than the subtending bracts; perianth ± granular-roughened on the outside; fruit a capsule

7. Margins of cauline leaves and bracts various (spiny in a few species); corolla of united petals; calyx usually none (except in Jasione), but a pappus of scales, awns, or bristles often present; stamens almost always fused in a ring around the style

8. Calyx absent, or represented by hairs, scales, or bristles, mostly irregular in number (mostly not 5), or a ring of tissue; fruit an achene

3. Petals separate; ovaries apparently 5 or more; stamens numerous, their filaments connate, at least for much of their length, into a tube around the style; leaves palmately veined (may be deeply lobed)

4. Leaves opposite; stamens 2 or 4; corolla bilaterally symmetrical or in a few genera essentially regular; stems usually 4-angled (“square”) and foliage often aromatic when bruised (“minty” or citrus-like)

7. Flowers with at least the carpels (often one or more other cycles as well) fewer than 5; corolla and leaves various (carpels 5 only in Dictamnus and sometimes Ruta, with alternate leaves and nearly entire leaflets)

11. Ovary deeply 4-lobed, appearing like 4 separate ovaries around the base of the single style [and also keyed as such], the fruit (1–) 4 nutlets; plants usually with a 4-angled (“square”) stem and often a minty or citrus-like aroma when bruised

1In the field, plants are usually readily recognized as being aquatic if one is not misled by a rise in water level to assume that a temporarily inundated plant belongs to a normally aquatic species. In the herbarium, a proper label should record the habitat, but most of the larger true aquatics, even without complete data, can be recognized as such by the delicate structure of submersed stem and leaves, which are often extremely limp and flexible; hence when dry they still convey the impression of having been supported by water. The presence of algae, other aquatic organisms, or marl encrustations is also a handy clue to an underwater source. Rush-like plants (grasses, sedges, rushes) with erect stems extending above the water should not be sought under this part of the key unless they have definite limp aquatic foliage. Aquatics producing only floating leaves, their petioles extending to roots or rhizomes in the substrate, will key here as well as elsewhere in the General Keys on the basis of their floral characters.

2Included in Key C are a few leafless or apparently leafless herbaceous plants which are not parasitic or saprophytic but might be sought here because of decided yellowish (or at least non-green) color of at least some individuals as well as apparently leafless condition at flowering time. Also included are herbaceous plants that flower when leafless.

3Key D is offered for certain plants that are obviously mature seed-plants (not ferns and their allies) but often produce sterile structures as described rather than flowers; specimens of these species, if they possess flowers, may also be run in the appropriate other portions of the General Keys.

4The plants in Key E are monocots, which usually have floral parts in 3’s (rarely 2’s, never 5’s) and parallel-veined leaves. The few monocots with apparently netted-veined leaves will also run in the alternative lead of this couplet, where all dicots belong, even those with apparently parallel-veined leaves. All plants not covered in keys A (aquatics), B (woody plants), and C & D (plants lacking green color or with inflorescences with bulbils or tufts of leaves) with flat ribbon-like, grass-like or sword-shaped, or ± terete linear-subulate leaves belong here, even if the veins are obscure, unless (1) perianth parts (sepals or petals or both) are present and 5, (2) the perianth is absent or chaffy with the stamens 1 or 4, or (3) the flowers are in an involucrate head (cf. Key F). All plants with rush-like stems and apparently leafless or the leaves bristle-like, 3-angled or involute, belong here. Only 4 non-monocots have flower parts uniformly in sets of 3|Asarum, Floerkea, Proserpinaca, and Rumex.

5All plants not covered in keys A–D with compound, deeply lobed, or toothed leaves belong here, as do all others (even monocots) with distinctly netted-veined leaves, i.e. with some main veins diverging from the midvein rather than all running from base to apex of blade. Also included here are the 3 numbered exceptional “parallel-veined” options excluded (in footnote 4) under the alternative lead (to Key E), but generally recognizable as dicots by having perianth parts in 5’s (commonly), a chaffy (or absent) perianth and 1 or 4 stamens, and/or an involucrate head.

6Each stamen and pistil in Euphorbia is anatomically a very much reduced single flower, as evidenced by the stalk of the ovary and a joint or swelling on the stalk of a stamen, marking the junction of a pedicel and filament.

7If perfect flowers are also found on a plant, try also the alternative lead. Some plants with flowers in which either the stamens or the pistils mature distinctly earlier than the other are included here as well as under perfect flowers, but users should be cautious on this point.

8Several genera and families are included for convenience here that technically have both corolla and calyx but in which one of these series either is tiny or vestigial and hence usually overlooked or falls off very early in anthesis.

9A few plants are included here in which the ovary position is so obscure in a technically perigynous flower as to be easily misinterpreted as inferior.

10Various plants might be sought here, including species of Poa and Festuca normally with some bulblets and others with deformed (diseased?) inflorescences.

11The flowers in Polygala superficially resemble those of the Fabaceae (“papilionaceous”) but the perianth parts are not parallel. Of the 5 sepals, the 2 lateral ones are large and petaloid (“wings”); the petals are 3, the lower one forming a “keel” (usually with a fringe or appendage near the end).

12The flowers in Impatiens include 3 sepals, of which the lower one is large, petaloid, sac-like, and slender-spurred; the petals are apparently 3, each of the 2 lateral ones with a lobe.

13Our genera of Lamiaceae having an ovary not deeply 4-lobed and which therefore will key here are Ajuga, Teucrium, and Trichostema.